1. Technical Field of the Invention
The present invention relates generally to flow visualization, and more particularly to off-surface flow visualization using infrared imaging.
2. Discussion of the Related Art
The visualization of off-surface flow fields plays an important role in the analysis of aerodynamic characteristics observed during flight and wind-tunnel testing of aircraft configurations. Visualization can help provide a more complete qualitative understanding of important off-surface flow phenomena such as vortical flow formation, location, and breakdown. Without visualization, off-surface flow-field characteristics can be very difficult to understand.
One type of off-surface flow, wingtip vorticity, occurs when the different air pressures of the upper and lower wing surfaces circulate about the wingtip area. This induced drag airflow causes the air to spiral past the wingtips and ultimately to form vortices behind the wing. In flight under high atmospheric humidity these vortices become visible, trailing downstream from near the wingtips, because of condensation of water vapor in the low-pressure vortex cores. This is an unsatisfactory method of visualizing off-surface flows because it only occurs at the wing-tips under particular atmospheric conditions.
Active techniques to view in-flight vortical flows involve introducing smoke into the flow. One current smoke flow visualization technique consists of utilizing a smoke bomb explosive device that lasts one minute. It is small in size and is mounted external to the aircraft surface. Being of an explosive nature, the smoke bomb must have electrical leads connected to it for detonation. This technique is active for a very short time period thus allowing for the visualization of only one vorticity pattern per flight and is not practical at high speeds. Additionally, the smoke bomb, because it is mounted to the outside of the aircraft, disrupts the flow phenomenon to be visualized.
Another current smoke flow visualization technique consists of a large apparatus powered by aircraft electrical current that heats kerosene to its burning point to create smoke. This apparatus must be located near the point of smoke injection, and because of its large size is impractical for many applications.
It is accordingly an object of the present invention to visualize off-surface flow phenomena.
It is another object of the present invention to visualize off-surface flow phenomena using a method which is located entirely within the aircraft.
It is another object of the present invention to visualize off-surface flow phenomena at various speeds and altitudes.
It is another object of the present invention to visualize an unlimited number of off-surface flow phenomena during a single flight.
It is yet another object of the present invention to accomplish the foregoing objects in a simple manner.
Additional objects and advantages of the present invention are apparent from the drawings and specification which follow.